A valve system for use with a cylinder having an extensible rod, includes first and second valve assemblies, each including an inlet/outlet port configured to selectively be coupled with a source of pressurized gas, a check valve biased toward a closed state and having a check valve body at least partially receivable within a first port of the cylinder, a flow control valve positioned in series between the inlet/outlet port and the check valve, and an inlet pilot port connected with the check valve for opening the check valve when supplied with pressurized gas. First and second pilot lines extend to the respective inlet pilot ports from respective outlet pilot ports of the opposite ones of the first and second valve assemblies. When pressurized gas is supplied to the inlet/outlet port of a valve assembly, pressurized gas is also supplied to the opposite inlet pilot port.

A system and method for detecting the functional state of a piloted or direct-operated isolation valve in a hydraulic circuit is presented. In some examples the hydraulic circuit is a steering circuit and the isolation valve provides selective isolation between a hydraulic actuator and one or more metering valves. In some examples, the isolation valve assembly is movable between a first position, in which fluid flow between the metering valve and the actuator is enabled, and a second position, in which fluid flow between the metering valve and the actuator is blocked. When the isolation valve assembly is moved to one of the first and second positions, an inlet port and a pressure sensing port of the isolation valve assembly are placed in fluid communication with each other. When the isolation valve assembly is moved to the other of the first or second position, a second inlet port and the pressure sensing port are placed in fluid communication.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.

A safety valve which has two fluidically interconnected safety valves, each of which has a 4/2-way valve function. Each safety valve has a first connecting port and a second connecting port, which are connected to each other in such a way that a fluid flow through the two safety valves, controlled by means of a control valve, to a fluid-actuated drive is prevented if the two safety valves simultaneously adopt a first switching position and such a fluid flow is possible if both valves simultaneously have a second switching state. One safety aspect results from the fact that the above-mentioned fluid flow is also prevented if the two safety valves adopt different switching states.

A construction machine that can easily regulate a set maximum flow rate at a time of replacement of an attachment and that can improve an energy conservation performance is provided. A controller selects a corresponding map in response to an attachment designation signal from among maps each of which sets a relationship between an operation signal per type of the attachment and a flow rate of a hydraulic fluid supplied to an actuator, generates a control signal by causing the selected map to refer to the operation signal, and controls a flow control valve of an attachment flow rate regulation valve device in such a manner that a position of the flow control valve is switched over from a neutral position on the basis of the control signal. An unloading valve that maintains a differential pressure across the flow control valve is disposed in the attachment flow rate regulation valve device.

A return manifold includes a housing having a first workport, a second workport, a third workport, and a fourth workport, and defining a first chamber and a second chamber. The return manifold includes a back-pressure disk arranged between the first workport and the first chamber, a bypass disk arranged between the first chamber and the second chamber, a back-pressure spring biased between the back-pressure disk and the bypass disk, and a bypass spring biased against the bypass disk. The back-pressure disk and the bypass disk are hydro-mechanically coupled so that movement of the bypass disk alters a force on the back-pressure disk and movement of the back-pressure disk alters a force on the bypass disk.

Distributed trailing edge wing flap systems are described. An example wing flap system for an aircraft includes a flap and an actuator. The flap is movable between a deployed position and a retracted position relative to a fixed trailing edge of a wing of the aircraft. The actuator is to move the flap relative to the fixed trailing edge. The actuator is hydraulically drivable via first pressurized hydraulic fluid to be supplied by a hydraulic system of the aircraft. The actuator is also hydraulically drivable via second pressurized hydraulic fluid to be supplied by a local power unit. The local power unit is selectively connectable to an electrical system of the aircraft. The electrical system is to power the local power unit to supply the second pressurized hydraulic fluid.

A work implement has a boom, an arm, and a bucket pivotable around a bucket axis which is a pivot axis with respect to the arm and a tilt axis orthogonal to the bucket axis. The hydraulic cylinder has the bucket pivot around the tilt axis. The regulation valve regulates an amount of supply of a hydraulic oil to be supplied to the hydraulic cylinder based on a command signal. The position sensor measures a stroke length of the hydraulic cylinder. The control unit resets the stroke length measured by the position sensor. The control unit determines proximity to a stroke end of the hydraulic cylinder, generates a command signal for increasing a degree of opening of the regulation valve in the proximity of the stroke end, and resets the stroke length measured by the position sensor while the regulation valve is open in response to the command signal.

Sod harvesters can have hydraulic systems that are configured to actuate components with precise timing. The hydraulic system of a sod harvester can be configured to maintain the temperature of hydraulic fluid both during harvesting and while harvesting is paused to thereby eliminate or minimize the occurrence of periods of variation in the timing of actuation of the components that the hydraulic fluid drives. As a result, these components can be consistently actuated with precise timing even after harvesting has been paused. Additionally, such configurations can minimize the amount of time required to warm the hydraulic fluid to a steady operational temperature.

A fluid power control system for load handling mobile equipment includes a pair of hydraulic actuators for moving respective cooperating load-engaging members selectively toward or away from each other, or in a common direction, at respective asynchronous speeds to selectively attain either synchronous or asynchronous respective positions of the actuators. The actuators have sensors enabling a controller to monitor their respective movements and correct unintended differences in the actuators' respective movements, such as unintended differences in relative intended positions, speeds, or rates of change of speeds. Respective hydraulic valves responsive to the controller separately and nonsimultaneously decrease respective flows through the respective actuators to more accurately and rapidly correct differences from the intended relative movements of the actuators.